NPL 1 relates to the specifications of the next generation packet switched (PS) network by SAE (System Architecture Evolution) of the 3GPP (3rd Generation Partnership Project). FIG. 21 is a diagram illustrating a part of a network configuration disclosed in NPL 1. A network 406 is a collection of IP-based networks, such as the Internet or an ISP (Internet Service Provider). An access network (EPC: Evolved Packet Core) 420 is an access network connected to the network 406. In the EPC 420, an access point (eNB or eNodeB) 402 and an eNB 412, which are wireless access points of a mobile terminal (UE: User Equipment) 100, and a gateway node (PGW: Packet data network GateWay) 416, which is a connection gateway of the network 406 and serves as a handover anchor point, are present.
A communication destination node 408 that can perform communication of IP packet data (hereinafter, simply referred to “data”) with the UE 100 is connected to the network 406. In the EPC 420, a signaling processing node (MME: Mobility Management Entity) 410 that processes signaling used in the EPC 420 is present. In the EPC 420, a relay node (SGW: Serving GateWay) 404 and an SGW 414 that relay data between the PGW 416 and the eNB 402 or the eNB 412 and perform a signaling process in the EPC 420 are present. Further, the PGW 416 also performs the signaling process in the EPC 420.
Handover of the UE 100 disclosed in NPL 1 is performed using the PGW 416 as an anchor point. Hereinafter, a handover processing method in the UE 100 will be described with reference to FIGS. 21 and 22.
As disclosed in NPL 1, a radio communication path (RB: Radio Bearer) is established between the UE 100 and the eNB 402. Each communication path (bearer) is established between the eNB 402 and the SGW 404 and between the SGW 404 and the PGW 416, and thus binding information of the communication paths are retained in the eNB 402 and the SGW 404. Further, the bearer established between the eNB and the SGW is referred to as an S1 bearer and the bearer established between the SGW and the PGW is referred to as an S5/S8 bearer.
The eNB 402 compares situations in which the UE 100 receives radio signals from the eNB 402 and a neighboring eNB and determines handover of the UE 100 (step s502). Next, by performing signaling transmission and reception between the SGW 414 and the eNB 412, the S1 bearer between the eNB 412 and the SGW 414 is established as a new communication path formed via the MME 410 and the S5/S8 bearer is established between the SGW 414 and the PGW 416 (step s504 to step s512). At this time, when the UE 100 switches a wireless connection destination from the eNB 402 to the eNB 412, RB is established between the UE 100 and the eNB 412 (step s514 to step s516).
The binding information of the RB and the S1 bearer is retained in the eNB 412 and the binding information of the S1 bearer and the S5/S8 bearer is retained in the SGW 414. Further, data having been transmitted to the eNB 402 is transmitted (not shown) to the eNB 412, while a data transmission path is established (not shown) between the eNB 402 and the eNB 412 via the SGW 404 and the SGW 414 during step s504 to step s516 and the UE 100 switches the connection destination from the eNB 402 to the eNB 412. When the UE 100 completely switches the connection destination to the eNB 412, a bearer updating process is completed in the EPC 420 (step s516 to step s528) and the handover of the UE 100 is completed.
NPL 1 does not support handover involving the change in the PGW. When the PGW is changed, an IP address allocated to the UE is also changed and a new bearer is also established. Therefore, session with the communication destination is disconnected. An example in which a gateway node is changed by movement of the UE is disclosed in NPL 2. NPL 2 discloses a case in which a UE connected locally to a house network (home network) from a home access point (HeNB: Home e NodeB) moves out of a house and attempts remote connection to the home network from an eNB which is an access point out of the house.
An example in which home network connection (local access) is attempted by performing wireless connection to the HeNB, as disclosed in NPL 2, will be described with reference to FIG. 23. A network 616 is an IP-based network and is the same as the network 406 described above. The EPC 632 connected to the network 616 and a node having the configuration of the EPC 632 are the same as the EPC 420 described above. In a house 630, an individual network (home network 614) of a home, a corporation, or the like is present.
The home network 614 is one of the IP-based networks and is connected to an external network 616 via a broadband router (BB router) 610. In the home network 614, an access point (HeNB) 602 which is a wireless access point of the UE 100 present in the house 630 and a local gateway node (L-PGW: Local Packet data network GateWay) 606, which is a local connection gateway of the home network 614 and serves as a handover anchor point, are present.
A communication destination node 612 performing data communication with the UE 100 is connected to the home network 614.
In the home network 614, a home gateway 608 that manages a node connected to the home network 614 and makes connection from the outside to the home network 614 via the network 616 is present. In the home network 614, a relay node (L-SGW: Local Serving GateWay) 604 that relays data between the L-PGW 606 and the HeNB 602 and performs signaling processing in the house 630 is also present. Further, the L-PGW 606 also performs the signaling processing with the EPC 632.
The HeNB 602 is connected to a termination node (a node (not shown) or the SGW 622) in the EPC 632 via the BB router 610 and the network 616. The UE 100 connected to HeNB 602 can communicate with the network 616 via the EPC 632. Further, the HeNB 602, the L-SGW 604, and the L-PGW 606 may be physically configured as a single node and is treated as an HeNB or may be treated as a single HeNB including the home gateway 608.
When the UE 100 connected to the HeNB 602 performs data communication with the communication destination node 612, a bearer is established among the UE 100, the HeNB 602, the L-SGW 604, and the L-PGW 606, as indicated by a dotted line in FIG. 24. The establish of this bearer is performed via the MME 620 of the EPC 632. When the bearer is established, the UE 100 acquires an IP address used in the home network 614 from the L-PGW 606. The UE 100 performs the data communication with the communication destination node 612 using this IP address.
On the other hand, when the UE 100 is connected to the eNB 624 and performs the data communication (remote access) with the communication destination node 612, a method of establishing a bearer between the eNB 624 and the L-PGW 606 is not described in the current 3GPP specification. Therefore, for example, as indicated by a one-dot chain line in FIG. 24, a bear is established via the eNB 624, the SGW 622, and the PGW 618. Then, the UE 100 acquires the IP address used in the network 616 from the PGW 618, is connected to the home gateway 608 via the network 616 and the BB router 610 and performs the data communication with the communication destination node 612 via the home gateway 608. The connection from the UE 100 to the home gateway 608 can be realized in accordance with a method of using a SIP (Session Initiation Protocol) or the like described in, for example, NPL 3.
The IP address allocated to the UE 100 is different between when the UE 100 is connected to the HeNB 602 and performs the data communication with the communication destination node 612 and when the UE 100 is connected to the eNB 624 and performs the data communication with the communication destination node 612. Therefore, the UE 100 performs a process in accordance with different data flows. Accordingly, a mobile IP is disclosed in NPL 4 and NPL 5 as a method of performing the process in accordance with the same data flow even when the IP address of the UE is changed. The mobile IP is a technology for enabling the UE to continue the communication using the same IP address by providing binding information of the IP address to a Home Agent node present in the midway of a communication path even when the IP address of the UE is changed. Accordingly, even when the UE 100 changes a connection destination from the HeNB 602 to the eNB 624 and continues the communication with the communication destination node 612, the UE 100 can perform the process in accordance with the same data flow as long as the function of the Home Agent node is provided to the home gateway 608 or the like.
However, since this method does not support the handover of the UE 100 disclosed in NPL 1, the UE 100 does not transmit data and transmission of the data to the UE 100 is thus interrupted during a process of switching the connection destination and a process of performing connection with the home gateway 608. Since the smallest interruption time is 1 second, this value may not be ignored in real-time communication.
In regard to the data transmission, for example, NPL 6 describes a method of transmitting the data to an access router of a handover destination during handover of a mobile terminal.
Further, PTL 1 discloses a method of continuously receiving a context using an access controller connected to a plurality of access networks, even when a mobile terminal is moved to another access network.